Systems and methods incorporating ionic liquids for electrochemically mediated capturing of lewis acid gases

ABSTRACT

The present invention generally relates to methods and systems for capturing a Lewis acid gas (e.g., CO 2 ). In some embodiments, the methods and systems utilize an ionic liquid incorporated into one or more electrochemical cells.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/660,587, filed Jul. 26, 2017, entitled “SYSTEMS AND METHODSINCORPORATING IONIC LIQUIDS FOR ELECTROCHEMICALLY MEDIATED CAPTURING OFLEWIS ACID GASES”, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/367,206, filed Jul. 27, 2016, each of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to methods and systems forcapturing Lewis acid gases, such as CO₂. In some embodiments, themethods and systems utilize an ionic liquid incorporated into one ormore electrochemical cells.

BACKGROUND OF THE INVENTION

There is often a need to remove Lewis acid gases from gas mixtures. Forexample, there is a long-term need to suppress CO₂ emissions from theburning of fossil fuels to avoid dangerous anthropogenic interferencewith the climate system. For example, in 2014, around 2.2 billion tonsof CO₂ were generated from coal-fired electric power plants in the US,representing 40% of the nation's emissions. There is, therefore, anecessity to stem this release by developing post-combustion carboncapture technologies, which may be added to new plants or retrofitted toexisting plants. One technology involves thermal amine scrubbing, whichuses cold solutions of amines to bind to CO₂ and reverses this bindingby elevating the temperature. This was recently implemented at theBoundary Dam power station in Canada, to capture up to 1 million tons ofCO₂ per year. However, associated with this process is a large enthalpyof reaction and a significant energy cost to release the CO₂, as well asheat lost to water vaporization (˜85 kJ mol⁻¹ at 40° C.). In addition,in many power plants (as well as non-power generating industrialprocesses) there is not always enough steam to operate a thermal swingsystem.

Accordingly, improved methods and systems are needed.

SUMMARY OF THE INVENTION

The present invention generally relates to methods and systems forcapturing designated gases. In some embodiments, the gas may be a Lewisacid gas (e.g., CO₂, SO₂, boranes, etc.). According to one or moreembodiments a system for capturing a Lewis acid gas (e.g., CO₂) isprovided. The system may comprise a first zone comprising a functionalionic liquid comprising a cation and an anion; and a second zone influid connection with the first zone comprising a complexation agentcapable of associating and/or disassociating the cation to and/or fromthe functional ionic liquid upon exposure to an electrical potential.

According to one or more embodiments, a method for capturing a Lewisacid gas (e.g., CO₂, SO₂, boranes, etc.) is provided. The method maycomprise providing a system comprising a first zone and a second zone influid connection with the first zone. The first zone may comprise afunctional ionic liquid comprising a cation and an anion. The secondzone may comprise a complexation agent capable of associating and/ordisassociating the cation to and/or from the functional ionic liquidupon exposure to an electrical potential. The method may furthercomprise exposing the ionic liquid to the Lewis acid gas in the firstzone, wherein the cation associates with the Lewis acid gas to form acation-Lewis-acid-gas complex: and exposing the cation-Lewis-acid-gascomplex to the complexation agent in the second zone, wherein thecomplexation agent associates with the cation to forma acation-complexation agent complex and the Lewis acid gas is released toform free Lewis acid gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents a process flow diagram of a method for capturing CO₂,according to one or more embodiments.

FIG. 2-FIG. 4 depict non-limiting systems of the present invention,according to some embodiments.

FIG. 5 depicts a non-limiting system of the present invention for use inthe conversion of CO₂ to a dissolved species, according to someembodiments.

FIG. 6 shows a plot of absorption and desorption of CO₂ in[HButylen][Tf₂N] at 35° C., 50° C., and 70° C.

FIG. 7 shows a plot of a cyclic voltammogram of [HButylen][Tf₂N] at 50°C. under N₂ at 10 mV/s with Cu working electrode, Pt counter electrodeand Ag|AgNO₃ reference electrode.

FIG. 8 shows a plot of the expected and experimentally determined numberof moles of CO₂ released in the headspace of the electrochemical cell,and the number of moles of Cu(II) produced.

Other aspects, embodiments, and features of the invention will becomeapparent from the following detailed description when considered inconjunction with the accompanying drawings. The accompanying figures areschematic and are not intended to be drawn to scale. For purposes ofclarity, not every component is labeled in every figure, nor is everycomponent of each embodiment of the invention shown where illustrationis not necessary to allow those of ordinary skill in the art tounderstand the invention. All patent applications and patentsincorporated herein by reference are incorporated by reference in theirentirety. In case of conflict, the present specification, includingdefinitions, will control.

DETAILED DESCRIPTION

The present invention generally relates to methods and systems forcapturing a gas, such as Lewis acid gases, including CO₂. In someembodiments, the methods and systems described herein utilize achemically reversible electrochemical reaction involving a complexationagent and an ionic liquid. In some cases, the complexation agent iscapable of associating a cation from the ionic liquid upon exposure toan electrical potential. In some cases, the complexation agent iscapable of dissociating a cation to the ionic liquid upon exposure to anelectrical potential.

According to one or more embodiments, the electrochemically-mediatedregeneration of ionic liquids described herein may be employed as anovel, cost-effective methods and systems to capture and/or remove aLewis acid gas (e.g., CO₂, SO₂, boranes, etc.) from a gas.

According to one or more embodiments, the electrochemically-mediatedregeneration of ionic liquids described herein may be employed as anovel, cost-effective methods and systems to capture and/or remove CO₂from a gas (e.g., a flue gas). According to one or more embodiments, gasdesorption (e.g., CO₂ desorption) is achieved through the oxidation of acopper electrode releasing cupric ions into the ionic liquidelectrolyte, which chelated to the ionic liquid cations and displacedLewis acid gas (e.g., CO₂), rather than through utilizing an energyintensive thermal swing to drive gas desorption.

While the description herein often makes reference to CO₂ as thespecific Lewis acid gas, a person of ordinary skill would understandthat this description could generally be applied to other Lewis acidgases, including, without limitation. SO₂ and boranes.

A non-limiting example of a scheme for capturing CO₂ using acomplexation agent and an ionic liquid is shown in FIG. 1. In thisfigure, the complexation agent is copper and the functional ionic liquidcomprises the cation of N-butylethylenediaminium. The complexation agentand ionic liquid should be viewed as exemplary, and those of ordinaryskill in the art will be able to apply the teachings of this scheme toother complexation agents and ionic liquids. Complexation agents andionic liquids are described in more detail herein.

In FIG. 1, cation 105, N-butylethylenediaminium which comprises anethylenediaminium group, of the functional ionic liquid is exposed toCO₂ 110 in a first zone, wherein the cation associates with the CO₂ toform cation-CO₂ complex 115. For example, the CO₂ may be scrubbed from aflue gas by the ionic liquid similar to those used in traditionalthermal scrubbing systems, where the first zone comprises a flue gasscrubbing zone.

Next, cation-CO₂ complex 115 is exposed to complexation agent 120 (e.g.,a copper-based complexation agent) in a second zone, wherein thecomplexation agent associates with the cation to form acation-complexation agent complex 125 and CO₂ is released to as free CO₂122. For example, the ionic liquid saturated with cation-CO₂ complexesmay be sent to an anode chamber of an electrochemical cell where acopper electrode is oxidized (corroded) to form cupric ions. These ionscomplex with the ionic liquid cation to form cation-complexation agentcomplex 125 and displace the CO₂ from the amine binding sites, therebyforming free CO₂ 122. The gas/liquid mixture may then be separated intoa pure CO₂ stream and the copper-saturated sorbent stream (i.e., thecomponent comprising the cation-copper complexes).

Next, cation-complexation agent complex 125 may be exposed to electricalcurrent 130, thereby reforming complexation agent 135 (e.g., copper) andcation 105 upon exposure to protons. For example, the copper-saturatedsorbent stream is directed to the cathode, where the cupric ions areexposed to electrical current (e.g., electrons 130) electroplated onto aseparate copper electrode, which regenerates the sorbent stream's CO₂absorbing capacity.

Without wishing to be bound by theory, ionic liquids disclosed hereincan bind to CO₂, or other Lewis acid gases, with the additionaladvantage that a thermal swing is not necessarily required fordesorption. Instead, desorption may be achieved by complexation toCu(II). By utilizing this process instead of aqueous amine solutions,many challenges including solvent evaporation and the need for asupporting electrolyte are eliminated. In addition, the use of an ionicliquid lowers the overpotential required to reduce the Cu(II) but, ifneeded, may be increased, due to the large electrochemical windows, todrive the reaction.

The term Lewis acid gas is given its ordinary meaning in the art andgenerally refers to a gas that is a chemical species that contains anempty orbital which is capable of accepting an electron pair. Notableexamples of Lewis acid gases include, without limitation: CO₂, SO₂, andboranes.

The term ionic liquid is given its ordinary meaning in the art andgenerally refers to salts that are in the liquid state below a selecttemperature, for example, 100° C. Generally, an ionic liquid comprises acation and an anion. Ionic liquids may be used for thermal scrubbingapplications due to their low volatility, high thermal stability,reduced potential for corrosion, and enhanced Lewis acid gas capacity.Ionic salts have negligible vapor pressure, good thermal stability andsolvation for a wide variety of gases. In particular relevance to anelectrochemically mediated system, the electrochemical windows of ionicliquids are exceptionally wide up to 6 V) as compared with water, whichhas an electrochemical window of 1 V). According to one or moreembodiments, functional ionic liquids incorporated into the systems andmethods disclosed herein may have chemical behavior that is analogous toamine solutions, but provide the advantages of serving as the sorbent,solvent, and the supporting electrolyte.

Without wishing to be bound by theory, while transition-metal salts areconventionally not very soluble in ionic liquids, it has been found thatgood dissolution can be achieved by complexing them with an ionicliquid. With this in mind, the electrochemistry presented herein is ofsignificant interest as it involves the rare occurrence ofelectrodeposition from an ionic liquid with a metal-containing cation.The above is beneficial to metal deposition because the electroactivespecies can easily access the electrode surface compared to the morecommon anionic metal complexes, which must travel against the electricfield and compete with other cations under reductive conditions, thusimproving energy efficiency of the process. Such chelate-based ionicliquids offer many advantages of being able to act as recyclablecatalysts for chemical transformations.

According to one or more embodiments a functional ionic liquid isprovided comprising a cation that both facilitates Lewis acid gas (e.g.,CO₂) capture and is capable of chelating to metal ions (e.g., cupricions).

In some embodiments, the cation of the functional ionic comprises aspecies represented by the structure shown in structural formula (I):

wherein:

R¹ has the formula: (C(R)₂)_(n), in which R is selected from the groupconsisting of H or optionally substituted C₁-C₃ alkyl; and n is 1, 2, 3,4, 5, or 6; and

R² has the formula: (C(R′)₂)_(m)—R″, in which R′ is selected from thegroup consisting of H or optionally substituted C₁-C₃ alkyl; R″ is H oroptionally substituted C₁-C₃ alkyl; and m is 1, 2, 3, 4, 5, 6, 7, 8, 9,or 10.

In some embodiments, R is selected from the group consisting of H orunsubstituted C₁-C₃ alkyl. In some embodiments, R′ is selected from thegroup consisting of H or unsubstituted C₁-C₃ alkyl. In some embodiments.R″ is selected from the group consisting of H or unsubstituted C₁-C₃alkyl. In some embodiments, R″ is unsubstituted C₁-C₁₀ alkyl. In someembodiments. R″ is optionally substituted C₁-C₅ alkyl. In someembodiments, R″ is unsubstituted C₁-C₅ alkyl. In some embodiments, R″ ismethyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, or t-butyl. In someembodiments, R″ is n-propyl. In some embodiments R″ is a carbocyclealkylgroup (cyclic hydrocarbon containing one or more double bonds), andcyclic hydrocarbon (heteroaryl). Heteroaryl groups include, for example,pyrrole, furan, thiophene, imidazole, oxazole, thiazole, pyrazole,pyridine, pyrazine, pyridazine, and pyrimidine, and the like. In someembodiments R″ is a vinyl group.

In some embodiments, the cation comprises an ethylenediaminium unit. Insome embodiments, the ethylenediaminium unit may be represented by thestructure shown in structural formula (II):

wherein R³ is any suitable group.

In some embodiments, R³ is selected from the group consisting of H,optionally substituted C₁ to C₁₀ alkyl, optionally substituted C₆ to C₁₀cycloalkyl, optionally substituted C₆ to C₁₂ aryl, optionallysubstituted alkenyl (e.g., vinyl groups such as —CHCHR″′, wherein R″′ isa suitable group, for example optionally substituted alkyl or optionallysubstituted aryl, including phenyl), and optionally substituted C₇ toC₁₂ alkyl. In some embodiments. R³ is optionally substituted C₁-C₁₀alkyl. In some embodiments. R³ is unsubstituted C₁-C₁₀ alkyl. In someembodiments, R³ is optionally substituted C₁-C₅ alkyl. In someembodiments, R³ is unsubstituted C₁-C₅ alkyl. In some embodiments, R³ ismethyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, or t-butyl. In someembodiments. R³ is n-propyl. In some embodiments R³ is a carbocyclealkylgroup (cyclic hydrocarbon containing one or more double bonds), andcyclic hydrocarbon (heteroaryl). Heteroaryl groups include, for example,pyrrole, furan, thiophene, imidazole, oxazole, thiazole, pyrazole,pyridine, pyrazine, pyridazine, and pyrimidine, and the like. In someembodiments R³ is a vinyl group.

Non-limiting examples of any of the above-referenced optionalsubstituents include OH, SH, SR^(i), SiH₃, Cl, Br, F, I, NH₂, CN, NO₂,COOR^(i), CHO, COC (ether), COR^(i) and OR^(i), wherein R^(i) is a C₁ toC₁₀ alkyl or cycloalkyl group. In embodiments where more than onesubstituent is present, the substituents may be the same or different.

In some embodiments the cation may be dicationic or polycationic. Forexample, (4-Vinyl)benzylethylene-diamine (VBEDA) may react with theappropriate acid to form an ionic liquid. The resulting monomer may be(co-)polymerized allowing for spin-coated or grafted layers, or thegeneration of sponges and thermoresponsive gels. Other polycations(which act as ionic liquid co-polymers) include polyimidazolium,polypyrrolidinium, polyallydimethylammonium,poly(3-acrylamidopropyl)trimethylammonium, amongst others. In the caseof polymeric ionic liquids anions may be combinations.

In some embodiments, the ionic liquid (IL) (e.g., ethylenediaminefunctionalized ionic liquid) may demonstrate good Lewis acid gas (e.g.,CO₂) absorption. According to some embodiments, ethylenediaminefunctionalized ionic liquid absorbs about 39 mg CO₂ per g IL at 35° C.According to one or more embodiments the electrolyte (which comprisesthe ionic liquid) is regenerated by electrodeposition of cupric ions atthe cathode.

Non-limiting examples of anions of the functional ionic liquid furtherinclude, without limitation: halide, sulfate, sulfonate, carbonate,bicarbonate, phosphate, nitrate, nitrate, acetate, triflate, nonaflate,bis(triflyl)amide, trifluoroacetate, heptaflurorobutanoate,haloaluminate, triazolide, amino acid derivatives (e.g. proline with theproton on the nitrogen removed), tetrafluoride, phosphorustetrafluoride, phosphorus hexafluoride, alkylsulfonate,fluoroalkylsulfonate, arylsulfonate, bis(alkylsulfonyl)amide,bis(fluoroalkylsulfonyl)amide, bis(arylsulfonyl)amide,(fluoroalkylsulfonyl)(fluoroalkylcarbonyl)amide, hydrogensulfate, alkylsulfate, aryl sulfate, carboxylate, hydrogen phosphate, dihydrogenphosphate, hypochlorite, or an anionic site of a cation-exchange resin.In some embodiments, the anion is boron tetrafluoride, phosphorushexafluoride, methanesulfonate, trifluoromethanesulfonate,benzenesulfonate, p-toluenesulfonate, bis(methanesulfonyl)amide,bis(trifluoromethanesulfonyl)amide, bis(benzenesulfonyl)amide, orbis(p-toluenesulfonyl)amide. In some embodiments, the anion ismethanesulfonate, trifluoromethanesulfonate, benzenesulfonate,p-toluenesulfonate, bis(methanesulfonyl)amide,bis(trifluoromethanesulfonyl)amide, bis(benzenesulfonyl)amide, orbis(p-toluenesulfonyl)amide. In some embodiments, the anion isbis(methanesulfonyl)amide, bis(trifluoromethanesulfonyl)amide,bis(benzenesulfonyl)amide, or bis(p-toluenesulfonyl)amide. In someembodiments, the anion is bis(trifluoromethanesulfonyl)amide or(trifluoromethanesulfonyl)(trifluoroacetyl)amide. In some embodiments,the anion is bis(trifluoroethanesulfonyl)amide.

In some embodiments these anions may be dianionic or polyanionic.Examples of possible polyanions include polyvinyl sulfonates,polyphosphates, polycarboxylates, poly(acrylamide)-2-methylpropanesulfonate, polyacrylic acid, as well as those havingtrifluoromethanesulfonamide anions in their backbone [Polymer, 2004, 45,1577-1582].

According to one or more embodiments the ionic liquid (e.g., functionalionic liquid) comprises N-butylethylenediaminium (“[HButylen]”) as thecation species and bis(trifluoromethanesulfonyl)amide (“[Tf₂N]”) as theanion species, having the structure shown in structural formula (III):

According to one or more embodiments, the system is also highly tunableallowing for improvements in physicochemical properties such asviscosity and also in gravimetric CO₂, or other Lewis acid gas,capacity.

In some embodiments, a mixture comprising a functional ionic liquid andone or more diluent liquids may be employed. In some embodiments, theintroduction of one or more diluent liquids may aid in reducing theviscosity, or altering the density, of the ionic liquid mixture (theresulting viscosity generally being a function of a linear mixingbehavior of the constituents), thereby allowing the process to takeplace at a lower temperature, where the process may be optimized forefficiency. In some embodiments, the diluent liquid may be a diluentionic liquid. In some embodiments the diluent liquid may compriseaqueous or non-aqueous solutions. In some embodiments the diluent liquidmay comprise amines (e.g., monoethanol amine). In some embodiments thediluent liquid may comprise water, acetonitrile, ethanol, methanol,diethyl ether, chloroform, dimethylsulfoxide, methylpyrrolidone,dimethyl formamide, acetone, toluene, benzene, hexane, pentane, aceticacid, cyclopentane, dioxane, ethyl acetat, 2-ethylhexyal acetate, butylacetate, benzyl benzoate, cottonseed oil, safflower oil, formic acid,acetic acid, etc., and any combinations thereof.

In some embodiments, a mixture comprising more than one ionic liquid maybe employed. A first ionic liquid (also referred to as a primary orfunctional ionic liquid) may comprise the cations principallyresponsible for forming the cation-Lewis-acid-gas complexes to aid incapturing the Lewis acid gas (e.g., CO₂). One or more additional ionicliquids, also referred to as secondary ionic liquids or diluent ionicliquids, may be present in the system to modify physicochemicalproperties of the system, such as viscosity or density.

Non-limiting anions for a diluent ionic liquid include, withoutlimitation: halide, sulfate, sulfonate, carbonate, bicarbonate,phosphate, nitrate, nitrate, acetate, PF₆ ⁻, BF₄ ⁻, triflate, nonaflate,bis(triflyl)amide, trifluoroacetate, heptaflurorobutanoate,haloaluminate, triazolide, and amino acid derivatives (e.g. proline withthe proton on the nitrogen removed). Non-limiting examples of cationsfor a diluent ionic liquid include, without limitation: imidazolium,pyridinium, pyrrolidinium, phosphonium, ammonium, sulfonium, thiazolium,pyrazolium, piperidinium, triazolium, pyrazolium, oxazolium,guanadinium, 1-butyl-3-methylimidazolium (“[bmim]”), pyridazinium,pyrimidinium, pyrazinium, imidazolium, and dialkylmorpholinium. Thediluent ionic liquid may comprise any combination of one or more anionsand cations from the lists above. In some embodiments, the diluent ionicliquid is [bmim][BF] and/or [bmim][PF₆].

In some embodiments, the ionic liquid mixture may comprise thefunctional ionic liquid at between 20% to 100% by weight, between 20% to80% by weight, between 30% to 70% by weight, between 30% to 60% byweight, or between 30% to 50% by weight, and the remainder being one ormore diluent liquids.

In some embodiments, the introduction of one or more diluent liquids mayaid in reducing the viscosity of the ionic liquid mixture (the resultingviscosity generally being a function of a linear mixing behavior of theconstituents), thereby allowing the process to take place at a lowertemperature, where the process may be optimized for efficiency. In someembodiments, the diluent liquid may be a diluent ionic liquid. In someembodiments the diluent liquid may comprise aqueous or non-aqueoussolutions. In some embodiments the diluent liquid may comprise amines(e.g., monoethanol amine). In some embodiments the diluent liquid maycomprise water, acetonitrile, ethanol, methanol, diethyl ether,chloroform, dimethylsulfoxide, methylpyrrolidone, dimethyl formamide,acetone, toluene, benzene, hexane, pentane, acetic acid, cyclopentane,dioxane, ethyl acetat, 2-ethylhexyal acetate, butyl acetate, benzylbenzoate, cottonseed oil, safflower oil, formic acid, acetic acid, etc.,and any combinations thereof.

The methods and/or systems may be utilized at any suitable temperature.In some embodiments, the methods and/or systems are operated at aboutroom temperature (e.g., about 25° C. In some embodiments, the methodsand/or systems are operated at a temperature between about 25° C. andabout 100° C. or between about 25° C. and about 90° C., or between about25° C. and about 80° C., or between about 25° C. and about 75° C.,between about 25° C. and about 70° C. A minimum temperature may be atemperature at which the ionic liquids remain liquids. According to someembodiments, the minimum temperature may be as low as −40° C., or insome cases even lower. A maximum temperature may be a temperature atwhich the components of the ionic liquid begin to breakdown, which takesplace according to some embodiments at a temperature between about 250°C. and about 300° C.

A number of non-limiting examples of systems of the present disclosurewill now be described in more detail. In some cases, a system comprisesa first zone and a second zone. The first zone may comprise a functionalionic liquid comprising a cation and an anion. The term functional ionicliquid refers to an ionic liquid comprising an ion that binds with aspecies of interest (e.g., CO₂). Where the term “ionic liquid” appearsherein, it may be understood that a functional ionic liquid is beingreferred to, unless the context in which the term appears suggests thata diluent ionic liquid is being described. The second zone may be influid connection with the first zone and comprise a complexation agentcapable of associating and/or disassociating the cation to and/or fromthe functional ionic liquid upon exposure to an electrical potential.The first zone and the second zone may be in the same container/area orthe two zones may be in different containers/areas which are in fluidconnection with each other (e.g., such that there may be flow from thefirst zone to the second zone and vice versa). In some embodiments, thefirst zone comprises a first compartment or portion of anelectrochemical cell and the second zone comprises a second compartmentor portion of the electrochemical cell. In some embodiments, the firstzone comprises a scrubber, and the second zone comprises a compartmentor portion of the electrochemical cell.

The complexation agent may be contained in the ionic liquid, may be aportion of the electrode, and/or may be associated with an electrode.

In some embodiments, the first zone and the second zone may be the same.The term “fluid communication” as used herein refers to two componentsor regions containing a fluid, where the components or regions areconnected together (e.g., by direct contact, or via a line, pipe,tubing, etc.) so that a fluid can flow between the two components orregions. Therefore, two chambers which are in “fluid communication” can,for example, be connected together by a line between the two chambers,such that a fluid or species present in the fluid can flow between thetwo chambers.

According to one or more embodiments. FIG. 2 shows the schematic of asystem in which the steps described with regard to FIG. 1 may beperformed. FIG. 2 shows a first zone 30 that comprises a functionalionic liquid comprising a cation and an anion. In the first zoneexposing the ionic liquid to CO₂ in the first zone, wherein the cationassociates with the CO₂ to form a cation-CO₂ complex. The complex may bedirected to a second zone 32 through a conduit 34. The second zone 32may comprise a complexation agent capable of associating and/ordisassociating the cation to and/or from the functional ionic liquidupon exposure to an electrical potential. In the second zone 32,cation-CO₂ complex may be exposed to the complexation agent, wherein thecomplexation agent associates with the cation to form acation-complexation agent complex and the CO₂ is released to form freeCO₂. An additional regeneration step may take place to restore thecation, which may then be directed back to the first zone via conduit36. Additional details made with regard to FIG. 1 may also apply to thesystem shown in FIG. 2 as would be understood by a person of ordinaryskill in the art.

FIG. 3 shows a non-limiting example of a system of the invention orcomponent thereof. For example, the electrochemical cell shown in FIG.3, may form the second zone 32 as represented in FIG. 2 and describedwith regard to FIG. 1. In FIG. 3, the system comprises container 2,first electrode 4 (e.g., anode) in electrical communication with secondelectrode 6 (e.g., cathode) via circuit 10, and ionic liquid 8,functioning as an electrolytic solution, in contact with both firstelectrode 4 and second electrode 6. Circuit 10 may optionally comprisecircuit component 11, e.g., power source, resistor, and/or capacitor.The system also comprises ion-permeable membrane 16 separating firstelectrode 4 from second electrode 6, and which allows for anions 12 tomove from the first electrode side to the second electrode side and/orcations 14 to move from the second electrode side the first electrodeside. Ion-migration balances the electroneutrality between the firstelectrode and the second electrode sides. The ionic liquid 8 containscomplexation agent 18 (represented by circles).

Advantageously, the system may also be regenerated between batches byapplication of a second electrical potential, wherein application of asecond electrical potential causes the complexation agent to return toits original form. It should also be understood that the system in FIG.3 could readily be employed in embodiments where the complexation agentforms the electrode or a portion of the electrode (e.g., a solidcomplexation agent).

A specific example of a system as described in FIG. 2 is shown in FIG.4. In FIG. 4, the system comprises a second zone 50 and a first zone 52in fluid communication by fluid conduits 54. The second zone 50comprises first electrode 56 (e.g., anode), second electrode 58 (e.g.,cathode), ionic liquid 60, and membrane 62 (e.g., ion exchangemembrane). In this figure, the complexation agent may be a portion of anelectrode and/or may be contained in the ionic solution.

In a non-limiting example of a complexation agent for use in FIG. 3, thesecond electrode may comprise Cu(OH)₂ (e.g., such that the reaction atthe second electrode is Cu(OH)₂+2e⁻→Cu+2OH⁻) and the first electrode maycomprise Cu (e.g., such that the reaction at the first electrode isCu+2OH⁻→Cu(OH)₂+2e⁻).

As used herein, a complexation agent generally refers to an agent (e.g.,chemical entity) which is capable of associating with and/ordissociating from a cation upon exposure to an electrical potential. Insome embodiments, the complexation agent is capable of associating witha cation upon exposure to a first electrical potential and is capable ofdissociating the cation upon exposure to a second electrical potentialwhich is more negative than the first electrical potential.Alternatively, in some embodiments, the complexation agent is capable ofassociating with a cation upon exposure to a first electrical potentialand is capable of dissociating the cation upon exposure to a secondelectrical potential which is more positive than the first electricalpotential. In some embodiments, the complexation agent is capable ofassociating a cation upon exposure to a first electrical potential andis capable of dissociating a cation upon exposure to a second electricalpotential which is more negative than the first electrical potential.Generally, the complexation agent exhibits such reversible behavior uponexposure to different potentials. In some embodiments, the cation is acation from an ionic liquid. As noted above, the complexation agent maybe provided in an ionic liquid, may be a portion of the electrode,and/or may change phases depending on its environment. Generally, thecomplexation agent is a capable of associate and/or dissociating with acation (e.g., from an ionic liquid) upon application of an electricalpotential to the complexation agent.

Those of ordinary skill in the art will be aware that each type ofcomplexation agent may require a different range of electricalpotentials to cause association and/or dissociation of a cation.

In some cases, the association and/or dissociation of a cation requiresan application of an electrical potential of about +/−0.1 volts, about+/−0.2 volts, about +/−0.3 volts, about +/−0.4 volts, about +/−0.5volts, about +/−0.6 volts, about +/−0.7 volts, about +/−0.8 volts, about+/−0.9 volts, about +/−1 volts, about +/−1.1 volts, about +/−1.2 volts,about +/−1.3 volts, about +/−1.4 volts, about +/−1.5 volts, about +/−1.6volts, about +/−1.7 volts about +/−1.8 volts, about +/−1.9 volts, about+/−2.0 volts, or about +/−2.5 volts. In some cases, the electricalpotential is less than that required for the oxidation of water (e.g.,−1.23 volts versus standard hydrogen electrode). In some embodiments,the application of the electrical potential is between about +/−0.1 andabout +/−2.5 volts, or between about +/−0.1 and about +/−2 volts, orbetween about +/−0.1 and about +/−1.5 volts, or between about +/−0.1 andabout +/−1 volts, or between about +/−0.5 and about +/−2.5 volts, orbetween about +/−0.5 and about +/−2 volts, or between about +/−1 andabout +/−2.5 volts, or between about +/−1 and about +/−2 volts. Those ofordinary skill in the art will be aware of suitable methods and systemfor applying an electrical potential to a complexation agent (e.g., withuse of a first electrode, a second electrode, and/or a power supply).

In some embodiments, the complexation agent is provided (e.g., as asolute) in an ionic liquid. The concentration of the complexation agentin the ionic liquid may be about 0.1 M, about 0.2 M, about 0.3 M, about0.4 M, about 0.5 M, about 0.6 M, about 0.7 M, about 0.8 M, about 0.9 M,about 1 M, about 1.2 M, about 1.4 M, about 1.5 M, about 1.75 M, about 2M, about 2.5 M, about 3 M, about 4 M, about 5 M, or greater. In someembodiments, the concentration of the complexation agent is betweenabout 0.1 M and about 5 M, or between about 0.1 M and about 4 M, orbetween about 0.1 M and about 3 M, or between about 0.1 M and about 2 M,or between about 0.1 M and about 1 M, or between about 0.5 M and about 3M, or between about 0.5 M and about 2 M.

In some embodiments, the complexation agent is provided as a solid. Insome cases, the complexation agent may be formed on the surface of asubstrate which is functioning as an electrode. In some cases, theelectrode may comprise the complexation agent. In some cases, theelectrode comprises the complexation agent, wherein at least about 10%,at least about 20%, at least about 30%, at least about 40%, at leastabout 50%, at least about 60%, at least about 70%, at least about 80%,at least about 90%, at least about 95%, at least about 98%, at leastabout 99%, or more, of the electrode by weight is the complexationagent.

The following equations describe non-limiting examples of complexationagents:

Cu+2OH⁻⇔CuO+H₂O+2e ⁻  (1)

Cu⇔Cu²⁺+2e ⁻E⁰=−0.34 (vs.SHE)  (2)

Cu²⁺+2OH⁻⇔Cu(OH)₂K_(sp)=2.2×10²⁰  (3)

Cu+2OH⁻⇔Cu(OH)₂+2e ⁻E⁰=0.27 (vs.SHE)  (4)

2Cu+O₂+H₂O⇔2Cu(OH)₂E⁰=0.67 (SHE)  (5)

In some embodiments, the complexation agent comprises Cu and/or CuO; Cuand/or Cu(OH)₂. In some embodiments, the complexation agent comprisesnickel and/or nickel-based species. In some embodiments, thecomplexation agent comprising zinc and/or zinc-based species.

In some embodiments, the systems and/or methods may be used inapplications involving gas scrubbing. Gas scrubbing is commonly employedto prevent the release of toxic chemicals (e.g., ammonia or hydrochloricacid) as well as greenhouse gases (e.g., carbon dioxide or sulfurdioxide) which are produced as byproduct in a variety of reactions.

In some embodiments, the systems and/or methods may be used inapplications, wherein the reaction involves the capture and/or releaseof CO₂. Such systems provide many advantages over current methods,including lower costs, increased efficiency (e.g., due to the need forless heating), the ability to operate under higher pressures (ifdesired), and/or fewer side products. In addition, the system may becapable of being regenerated.

In some embodiments, a system/method for the capture of CO₂ from gaseousstreams containing a mixture of gases is provided wherein at least aportion of the system/method comprises the conversion of CO₂ (e.g., to adissolved species). Such systems may comprise the use of an amine (e.g.,an ethylenediamine) in the functional ionic liquid. When the amine ispresent in the ionic liquid, the CO₂ and the amine can associate to forman amine-CO₂ complex. As a specific example of such a system, theprocess may comprise a complexation agents comprising copper. As will beknown to those of ordinary skill in the art, Cu(II) is capable ofcoordinating with ligands containing amine groups. When removing Cu(II)from the solution, either Cu(I) species or Cu(0) could be formed toreduce the competition for CO₂.

A non-limiting system can operate as follows and as illustrated in FIG.5. A feed gas comprising CO₂ and other gaseous materials (e.g., N₂) isprovided by inlet 200 and is flowed through column 202 which comprisesan ionic liquid comprising primary functional amine cation species andout through outlet 201. During the flow through the column absorption ofCO₂ via association with the amine cation to form an amine cation-CO₂complex 6. The resulting complex is provided to anode container 204containing anode 206. For example, the ionic liquid containing thecomplex may be flowed to anode container 204 via fluid connectors 208.The system may optionally comprise a pump (e.g., 215) which can be usedto circulate the ionic liquid throughout the system. In this example,anode 206 comprises Cu(0). Upon application of an electrical potentialto anode 206, Cu(II) ions may form. The Cu(II) ions may react with theCO₂-cation complex present in the ionic liquid, thereby causing CO₂ tobe released and a copper-cation complex to form. This ionic liquid canbe provided, optionally via flash tank 218 (e.g., to allow release andcollection of CO₂ gas) to cathode container 212 comprising cathode 214.For example, the ionic liquid containing CO₂-cation complex may be flownvia fluid conduit 216 to flash tank 208 wherein the CO₂ rich gas may becollected (e.g., via outlet 210), followed by flowing the ionic liquidvia fluid conduit 218 to cathode container 212. Cathode container 214and anode container 204 may be optionally separated by membrane 213. Incathode container 212, application of an electric potential can causethe copper-cation complex to dissociate, thereby reforming Cu(0) andregenerating the cation of the functional ionic liquid. Accordingly.FIG. 5 illustrates a regenerable system for the collection of CO₂ gas.

Those of ordinary skill in the art will be able to select othermaterials and reaction to which the above described systems/methods maybe used.

In some embodiments, an electrode is utilized comprising a porousmaterial, wherein the complexation agent intercalates into and/orde-intercalated from the electrode during operation of a system and/or amethod. The term intercalate is given its ordinary meaning in the artand refers to the ability of an ion (e.g., a complexation agent such ascopper) to insert into an electrode. An ion is said to reversiblyintercalate if it can de-intercalate (e.g., deinsert), without undulystressing the electrode, so that electrode performance is maintainedover repeated cycling. For example, in some embodiments, the electrodecomprises a porous material and the complexation agent (e.g., comprisingcopper) reversibly intercalates into the electrode by plating on thesurface (e.g., include any pores, if present). In some embodiments, boththe anode and the cathode are constructed such that complexation agentreversibly intercalates.

In some embodiments, use of a porous electrode as anintercalation/de-intercalation material for the complexation agentprovides many advantages over use of a solid electrode with asolubilized complexation agent and/or an electrode formed of thecomplexation agent. For example, utilizing aintercalation/de-intercalation material may significantly improve thecycling stability of a system and/or a method, as the porous structureimproves order and/or reversibility of the system and/or method ascompared to use of a solid electrode formed of the complexation materialand/or an electrode formed of material other than the complexationagent, wherein the complexation agent associates and/or dissociates fromthe outer surface of the electrode (e.g., a non-porous electrode).

The porous electrode may be made of any suitable material and/or maycomprise any suitable shape or size. In a non-limiting embodiment, theelectrode comprises a porous carbonaceous material. The termcarbonaceous material is given its ordinary meaning in the art andrefers to a material comprising carbon or graphite that is electricallyconductive. Non-limiting example of carbonaceous materials includecarbon nanotubes, carbon fibers (e.g., carbon nanofibers), and/orgraphite. It should be understood that an electrode that comprises acarbonaceous material may be an electrode which consists or consistsessentially of the carbonaceous material, or may be an electrode inwhich only a portion of the electrode comprises a carbonaceous material.For example, at least a portion of the electrode in electrical contactwith the electrolyte may comprise a carbonaceous material. In suchembodiments, the electrode may be partially fabricated from thecarbonaceous material or the carbonaceous material may be deposited overan underlying material. The underlying material generally comprises aconductive material, for example, a metal. Other non-limiting examplesof conductive materials are described herein.

In some embodiments, an electrode is porous. The porosity of anelectrode may be measured as a percentage or fraction of the void spacesin the photoactive electrode. The percent porosity of an electrode maybe measured using techniques known to those of ordinary skill in theart, for example, using volume/density methods, water saturationmethods, water evaporation methods, mercury intrusion porosimetrymethods, and nitrogen gas adsorption methods. In some embodiments, theelectrode may be at least about 10% porous, at least about 20% porous,at least about 30% porous, at least about 40% porous, at least about 50%porous, at least about 60% porous, or greater. The pores may be openpores (e.g., have at least one part of the pore open to an outer surfaceof the electrode and/or another pore) and/or closed pores (e.g., thepore does not comprise an opening to an outer surface of the electrodeor another pore). In some cases, the pores of an electrode may consistessentially of open pores (e.g., the pores of the electrode are greaterthan at least 70%, greater than at least 80%, greater than at least 90%,greater than at least 95%, or greater, of the pores are open pores). Insome cases, only a portion of the electrode may be substantially porous.For example, in some cases, only a single surface of the electrode maybe substantially porous. As another example, in some cases, the outersurface of the electrode may be substantially porous and the inner coreof the electrode may be substantially non-porous. In a particularembodiment, the entire electrode is substantially porous.

In some embodiments, the ionic liquid functions as an electrolyte. Anelectrolyte, as known to those of ordinary skill in the art, is anysubstance containing free ions that is capable of functioning as anionically conductive medium.

Various components of a system, such as the electrode, power source,electrolyte, separator, container, circuitry, insulating material, gateelectrode, etc. can be fabricated by those of ordinary skill in the artfrom any of a variety of components, as well as those described in anyof those patent applications described herein. Components may be molded,machined, extruded, pressed, isopressed, infiltrated, coated, in greenor fired states, or formed by any other suitable technique. Those ofordinary skill in the art are readily aware of techniques for formingcomponents of system herein.

In some embodiments, a system comprises at least one electrode, or atleast two electrode, or two electrodes. In some cases, an electrodecomprises a complexation agent, as described herein. In embodiments,wherein the electrode is not formed of the complexation agent, anelectrode may comprise any material that is substantially electricallyconductive. The electrode may be transparent, semi-transparent,semi-opaque, and/or opaque. The electrode may be a solid, semi-porous orporous. Non-limiting examples of electrodes include indium tin oxide(ITO), fluorine tin oxide (FTO), glassy carbon, metals,lithium-containing compounds, metal oxides (e.g., platinum oxide, nickeloxide), graphite, nickel mesh, carbon mesh, and the like. Non-limitingexamples of suitable metals include gold, copper, silver, platinum,nickel, cadmium, tin, and the like. In some instances, the electrode maycomprise nickel (e.g., nickel foam or nickel mesh). The electrodes mayalso be any other metals and/or non-metals known to those of ordinaryskill in the art as conductive (e.g., ceramics). The electrode may be ofany size or shape. Non-limiting examples of shapes include sheets,cubes, cylinders, hollow tubes, spheres, and the like. The electrode maybe of any size. Additionally, the electrode may comprise a means toconnect the electrode to another electrode, a power source, and/oranother electrical device.

Various electrical components of system may be in electricalcommunication with at least one other electrical component by a meansfor connecting. A means for connecting may be any material that allowsthe flow of electricity to occur between a first component and a secondcomponent. A non-limiting example of a means for connecting twoelectrical components is a wire comprising a conductive material (e.g.,copper, silver, etc.). In some cases, the system may also compriseelectrical connectors between two or more components (e.g., a wire andan electrode). In some cases, a wire, electrical connector, or othermeans for connecting may be selected such that the resistance of thematerial is low. In some cases, the resistances may be substantiallyless than the resistance of the electrodes, electrolyte, and/or othercomponents of the system.

In some embodiments, a power source may supply DC voltage to a system.Non-limiting examples include batteries, power grids, regenerative powersupplies (e.g., wind power generators, photovoltaic cells, tidal energygenerators), generators, and the like. The power source may comprise oneor more such power supplies (e.g., batteries and a photovoltaic cell).In a particular embodiment, the power supply is a photovoltaic cell.

In some embodiments, a system may comprise a separating membrane (e.g.,within an electrochemical cell). A separating membrane may be made ofsuitable material, for example, a plastic film. Non-limiting examples ofplastic films included include polyamide, polyolefin resins, polyesterresins, polyurethane resin, or acrylic resin and containing lithiumcarbonate, or potassium hydroxide, or sodium-potassium peroxidedispersed therein. In some cases, the membrane may be an anion exchangemembrane and/or cation exchange membrane (i.e., ones with anion and/orcation exchangeable ions) which are readily available from commercialsources. Non-limiting examples of anionic exchange membranes includepoly(ethylene-co-tetrafluoroethylene),poly(hexafluoropropylene-co-tetrafluoroethylene),poly(epichlorhydrin-ally glycidyl ether), poly(ether imide),poly(ethersulfone) cardo, poly(2,6-dimethyl-1,4-phenylene oxide),polysulfone, or polyethersulfone, associated with a plurality ofcationic species (e.g., quaternary ammonium groups, phosphonium groups,etc.).

A container may be any receptacle, such as a carton, can, or jar, inwhich components of a system may be held or carried. A container may befabricated using any known techniques or materials, as will be known tothose of ordinary skill in the art. For example, in some instances, thecontainer may be fabricated from gas, polymer, metal, and the like. Thecontainer may have any shape or size, providing it can contain thecomponents of the system. Components of the system may be mounted in thecontainer. That is, a component (e.g., an electrode) may be associatedwith the container such that it is immobilized with respect to thecontainer, and in some cases, is supported by the container. A componentmay be mounted to the container using any common method and/or materialknown to those skilled in the art (e.g., screws, wires, adhesive, etc.).The component may or might not physically contact the container. In somecases, an electrode may be mounted in the container such that theelectrode is not in contact with the container, but is mounted in thecontainer such that it is suspended in the container.

Reagents may be supplied to and/or removed from a system using acommonly known transport device. The nature of the reagent delivery mayvary with the type of fuel and/or the type of device. For example,solid, liquid, and gaseous reagents may all be introduced in differentmanners. The reagent transport device may be a gas or liquid conduitsuch as a pipe or hose which delivers or removes fuel, such as hydrogengas or methane, from the system and/or from the reagent storage device.Alternatively, the system may comprise a movable gas or liquid storagecontainer, such as a gas or liquid tank, which may optionally bephysically removed from the system after the container is filled withreagent.

As used herein, the term “alkyl” is given its ordinary meaning in theart and may include saturated aliphatic groups, including straight-chainalkyl groups, branched-chain alkyl groups, cycloalkyl (alicyclic)groups, alkyl substituted cycloalkyl groups, and cycloalkyl substitutedalkyl groups. In certain embodiments, a straight chain or branched chainalkyl has about 30 or fewer carbon atoms in its backbone (e.g., C₁-C₃₀for straight chain, C₃-C₃₀ for branched chain), and alternatively, about20 or fewer. Likewise, cycloalkyls have from about 3 to about 10 carbonatoms in their ring structure, and alternatively about 5, 6 or 7 carbonsin the ring structure.

The term “heteroalkyl” is given its ordinary meaning in the art andrefers to alkyl groups as described herein in which one or more atoms isa heteroatom (e.g., oxygen, nitrogen, sulfur, and the like).

The term “alkenyl” is given its ordinary meaning in the art and refersto unsaturated aliphatic groups analogous in length and possiblesubstitution to the alkyls described above, but that contain at leastone double or triple bond, respectively. In certain embodiments, thealkyl and alkenyl groups employed in the invention contain 1-20aliphatic carbon atoms. In certain other embodiments, the alkyl andalkenyl groups employed in the invention contain 1-10 aliphatic carbonatoms.

The term “aryl” is given its ordinary meaning in the art and refers tosingle-ring aromatic groups such as, for example, 5-, 6- and 7-memberedsingle-ring aromatic groups. The term “heteroaryl” is given its ordinarymeaning in the art and refers to aryl groups as described herein inwhich one or more atoms is a heteroatom (e.g., oxygen, nitrogen, sulfur,and the like). Examples of aryl and heteroaryl groups include, but arenot limited to, phenyl, pyrrolyl, furanyl, thiophenyl, imidazolyl,oxazolyl, thiazolyl, triazolyl, pyrazolyl, pyridinyl, pyrazinyl,pyridazinyl and pyrimidinyl, and the like. It should be understood that,when aryl and heteroaryl groups are used as ligands coordinating a metalcenter, the aryl and heteroaryl groups may have sufficient ioniccharacter to coordinate the metal center. For example, when a heteroarylgroup such as pyrrole is used as a nitrogen-containing ligand, asdescribed herein, it should be understood that the pyrrole group hassufficient ionic character (e.g., is sufficiently deprotonated to definea pyrrolyl) to coordinate the metal center. In some cases, the aryl orheteroaryl group may comprise at least on functional group that hassufficient ionic character to coordinate the metal center, such as abiphenolate group, for example.

As used herein, the term “substituted” is contemplated to include allpermissible substituents of organic compounds, “permissible” being inthe context of the chemical rules of valence known to those of ordinaryskill in the art. In some cases, “substituted” may generally refer toreplacement of a hydrogen with a substituent as described herein.However, “substituted.” as used herein, does not encompass replacementand/or alteration of a key functional group by which a molecule isidentified. e.g., such that the “substituted” functional group becomes,through substitution, a different functional group. For example, a“substituted phenyl” group must still comprise the phenyl moiety andcannot be modified by substitution, in this definition, to become, e.g.,a cyclohexyl group. In a broad aspect, the permissible substituentsinclude acyclic and cyclic, branched and unbranched, carbocyclic andheterocyclic, aromatic and nonaromatic substituents of organiccompounds. Illustrative substituents include, for example, thosedescribed herein. The permissible substituents can be one or more andthe same or different for appropriate organic compounds. For purposes ofthis invention, the heteroatoms such as nitrogen may have hydrogensubstituents and/or any permissible substituents of organic compoundsdescribed herein which satisfy the valencies of the heteroatoms. Thisinvention is not intended to be limited in any manner by the permissiblesubstituents of organic compounds.

Examples of substituents include, but are not limited to, lower alkyl,lower aryl, lower aralkyl, lower cyclic alkyl, lower heterocycloalkyl,hydroxy, lower alkoxy, lower aryloxy, perhaloalkoxy, aralkoxy, lowerheteroaryl, lower heteroaryloxy, lower heteroarylalkyl, lowerheteroaralkoxy, azido, amino, halogen, lower alkylthio, oxo, loweracylalkyl, lower carboxy esters, carboxyl, -carboxamido, nitro, loweracyloxy, lower aminoalkyl, lower alkylaminoaryl, lower alkylaryl, loweralkylaminoalkyl, lower alkoxyaryl, lower arylamino, lower aralkylamino,lower alkylsulfonyl, lower-carboxamidoalkylaryl, lower-carboxamidoaryl,lower hydroxyalkyl, lower haloalkyl, lower alkylaminoalkylcarboxy-,lower aminocarboxamidoalkyl-, cyano, lower alkoxyalkyl, lowerperhaloalkyl, lower arylalkyloxyalkyl, and the like.

The following examples are intended to illustrate certain embodiments ofthe present invention, but do not exemplify the full scope of theinvention.

Example 1

In a non-limiting example, ionic liquids were synthesized and tested.

[HButylen][Tf₂N] was synthesized via acid-base neutralization ofstarting materials. Fundamental physicochemical properties were firstinvestigated as they are essential when considering scale-up andapplication. Differential scanning calorimetry provided evidence of amelting point around 33° C. (which could be tuned by control of thecation architecture). Through thermogravimetric analysis (TGA) T_(onset)was determined to be 329° C. The high thermal stability is typical ofionic liquids containing the [Tf₂N] anion. Finally, the density. ρ, wasmeasured as a function of temperature. At 40° C. the density wasmeasured to be 1.355 g cm⁻¹ and the ionic liquid had a thermal expansioncoefficient, α_(p)=7.66×10-4° C. Importantly, for considering anyapplication this value is relatively small.

N-hexylethylenediaminium bis(trifluoroethanesulfonyl)amide wassynthesized and tested. It was found to have a melting point below −40°C., and a density of 1.31 g cm⁻³ at 40° C. Because of the low meltingpoint, this ionic liquid may be utilized at room temperature, if sodesired.

Example 2

In a non-limiting example, the reaction of the ionic liquid,[HButylen][Tf₂N], (described in Example 1) was demonstrated bythermogravimetric analysis, as shown in the graph in FIG. 6. Generally,two moles of ionic liquid bind with 1 mole of CO₂. Complete chemicalabsorption would lead to a gravimetric capacity of 55.4 mg of CO₂ per gIL. In addition, heavy fluorinated anion also allows for enhancedphysical absorption due to weak halogen bonds with CO₂. At 35° C. a 3.5%increase in mass is observed (though after 600 minutes a plateau was notyet reached), equating to 0.703 moles of CO₂ per two moles of IL. Thisis lower than a predicted 2:1 molar absorbance reflecting the finitetemperature-dependent reversibility of the reaction, and is highlightedat higher temperatures. However, it is clear that this capacity wasobtained rapidly.

Example 3

The cyclic voltammogram of [HButylen][Tf₂N] at 50° C. (due to m.p, andviscosity considerations) in FIG. 7 shows two redox couples, one at 0.02V corresponding to the Cu(II)|Cu(I) and another at −1.01 V correspondingto Cu(I)|Cu(0). The copper working electrode is corroded (oxidized) toCu(I) which is released to the diffusion layer of the electrode and isthen oxidized to Cu(II) which is chelated by the cation of the ionicliquid [23]. The copper in this complex is later reduced to Cu(I), whichresults in the dissociation of [Cu(Butylen)₂][Tf₂N]₂ complex andsubsequently Cu(I) is reduced to Cu(0) and is deposited onto the copperworking electrode or precipitates as fine copper particles. Therefore,an electrochemical window wider than ˜1V is sufficient to effect thecorrosion of the copper electrode to Cu(II), however, a larger potentialdifference was used in the release experiment to achieve higher rates ofrelease due to the larger overpotential.

Example 4

In a non-limiting example, TGA results indicate that saturation of[HButylen][Tf₂N] with CO₂ at temperature between 50° C. and 70° C. isachieved within 30 minutes. After two hours of purging in anelectrochemical cell, the ionic liquid was fully saturated and thepressure in the headspace reached a constant value after sealing thecell and the electrochemical corrosion of the copper electrode wasstarted after 5 minutes. A voltage of 3.5 V was applied across the cell,with copper as the positive electrode and a constant current of 11.5 mAwas rapidly achieved and maintained throughout the experiment.

The pressure in the headspace increased due to the release of CO₂ andthis change in pressure was used to calculate the number of moles of CO₂released, shown in FIG. 8. As shown in FIG. 1, for every Cu(II)generated, two molecules of CO₂ are released. The number of moles ofCu(II) produced is shown in FIG. 8, this was calculated from the totalcharge passed through the electrolyte, while the expected number ofmoles of CO₂ to be released is shown by the blue line.

TGA results show that at the maximum uptake of CO₂ at 50° C. and 70° C.is 2.97 wt % and 0.97 wt % respectively. By interpolation, it can beassumed that at 65° C. the CO₂-saturated RTIL contained ˜1.5 wt % CO₂.This amounts to 0.495 g (12.4 mmol) of CO₂. The curve of the moles ofCO₂ released, shown in FIG. 8, shows an initial release of CO₂ slightlylarger than expected, which could be due to the release of some of thephysisorbed CO₂ along with the chemisorbed CO₂. However, the curve showsa constantly declining rate of release and after two hours, only about10% of the captured CO₂, as predicted by TGA results, is released. Also,the number of moles of CO₂ released after 60 minutes are less thanexpected given the number of moles of Cu(II) ions produced by theoxidation of the copper electrode, calculated from the total charge inthe experiment. This is due to the recapture of some of the released CO₂by the newly regenerated ionic liquid molecules which lose theirchelated Cu(II) ion to reduction at the platinum counter electrode. Asthe system reaches equilibrium, there will be a constant flux of Cu(II)ions between the copper electrode, where they are generated, and theplatinum counter electrode, where they are electroplated andsubsequently removed from the ionic liquid electrolyte freeing two ionicliquid molecules to recapture the newly released CO₂. This will resultin plateauing of the headspace pressure, i.e. the moles of CO₂ released,as the rates of release and recapture balance. FIG. S9 shows thedeposited (electroplated) copper on the platinum electrode after the twohour-long experiment. Furthermore, as the pressure of CO₂ in theheadspace increases, the vapor-liquid equilibrium (VLE) is shifted tofavor the dissolution of more CO₂ into the electrolyte.

The problem of the declining rate of release is an artifact of the batchand sealed experimental setup in this work, in some embodiments, may becircumvented by separating the platinum counter electrode from the ionicliquid electrolyte in glass vial with a porous membrane which contains asolution of sacrificial reduction compound, such as benzoquinone, whichcan be reduced at the electrode in lieu of the Cu(II) ions that aregenerated due to the corrosion of the copper working electrode. In whichcase, the overall concentration of Cu(II) ions in the ionic liquidelectrolyte increases with time at a constant rate that is proportionalto the current passing through the cell and thus most of the capturedCO₂ can be released, also at a constant rate (ignoring reabsorption).However, this is not expected to manifest in the continuous and opensystem since the flow in their reported system involves a constantCu(II) ion concentration in the release chamber half-cell, as thegenerated ions are constantly advected away from the corroding electrodein the anode half-cell, where CO₂ is released, to the reducing(electroplating) electrode in the cathode half cell, where EDA isregenerated.

Example 5

In a non-limiting example, Values for the viscosity of the ionic liquid,[HButylen][Tf₂N], were measured at different temperatures. Viscosity isa parameter that affects the mass transport of both CO₂ and Cu ions. Themagnitude of the activation energy (Ea) is an indication of thedifficulty of transfer of molecules through the liquid matrix.

A rheometer, fitted with a cone and plate (2°/40 mm), was used todetermine viscosities between 40 and 100° C. First, viscosity wasmeasured as a function of shear stress (10-1000 Pa) at 40° C. to ensurethe materials gave linear responses with no shear history. Measurementswere then repeated at 50, 60, 70, 80, 90, 100° C. Once Newtonianbehavior was verified, the viscosities were recorded as a function oftemperature under constant shear stress. The resulting values ofviscosity for a given temperature are shown in Table 1 below:

TABLE 1 Temperature Viscosity (° C.) (Pa s) 40 0.182 50 0.100 60 0.06570 0.043 80 0.030 90 0.021 100 0.016

Like most ionic liquids [HButylen][Tf₂N] exhibited Newtonian behavior inthe range studied. It has a viscosity at 40° C. at around 182 cP.Surprisingly, however, the viscosity falls off rapidly with temperatureand at 100° C. is only 16 cP (similar to that of ethylene glycol).

In order to calculate the activation energies for viscous flow from theArrhenius Equation (Equation 6), semi-logarithmic Arrhenius-like plotswere made. In Equation 6, η represents viscosity, R is the universal gasconstant and T is the temperature.

$\begin{matrix}{\eta = {\eta_{\infty}\exp^{\frac{E_{a}}{RT}}}} & (6)\end{matrix}$

The activation energy for viscous flow has been calculated to be Ea=39kJ mol⁻¹.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified unless clearly indicated to the contrary. Thus,as a non-limiting example, a reference to “A and/or B,” when used inconjunction with open-ended language such as “comprising” can refer, inone embodiment, to A without B (optionally including elements other thanB); in another embodiment, to B without A (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list. “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one.” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently. “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one. A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying.” “having,”“containing,” “involving,” “holding,” and the like are to be understoodto be open-ended, i.e., to mean including but not limited to. Only thetransitional phrases “consisting of” and “consisting essentially of”shall be closed or semi-closed transitional phrases, respectively, asset forth in the United States Patent Office Manual of Patent ExaminingProcedures, Section 2111.03.

1-51. (canceled)
 52. A system for capturing a Lewis acid gas, comprising: a first zone for containing a functional ionic liquid comprising a cation and an anion; a second zone in fluid connection with the first zone for containing a complexation agent capable of associating and/or disassociating the cation to and/or from the functional ionic liquid upon exposure to an electrical potential; and apparatus constructed and arranged to apply an electrical potential to a complexation agent in the second zone.
 53. The system of claim 52, wherein the first zone contains the functional ionic liquid comprising a cation and an anion.
 54. The system of claim 52, wherein the second zone contains the complexation agent capable of associating and/or disassociating the cation to and/or from the functional ionic liquid upon exposure to an electrical potential.
 55. The system of claim 52, further comprising an inlet for receiving a gas comprising the Lewis acid gas into the first zone, and an outlet for delivering the Lewis acid gas.
 56. The system according to claim 52, wherein the Lewis acid gas is selected from the group consisting of CO₂, SO₂, and boranes.
 57. The system according to claim 52, wherein the cation of the functional ionic liquid is represented by the following structural formula:

wherein: R¹ has the formula: (C(R)₂)_(n), in which R is H or a C₁-C₃ alkyl group; and n is 1, 2, 3, 4, 5, or 6; and R² has the formula: (C(R)₂)_(m)—R″, in which R′ is H or a C₁-C₃ alkyl group; R″ is H or a C₁-C₃ alkyl group; and m is 1, 2, 3, 4, 5, 6, 7, 8, 9, or
 10. 58. The system according to claim 57, wherein n is
 2. 59. The system according to claim 58, wherein R is H.
 60. The system according to claim 57, wherein m is 6 and R″ is H.
 61. The system according to claim 57, wherein R² is 2-ethylhexyl.
 62. The system according to claim 52, wherein the anion of the functional ionic liquid is selected from the group consisting of boron tetrafluoride, phosphorus tetrafluoride, phosphorus hexafluoride, alkylsulfonate, fluoroalkylsulfonate, arylsulfonate, bis(alkylsulfonyl)amide, bis(fluoroalkylsulfonyl)amide, bis(arylsulfonyl)amide, (fluoroalkylsulfonyl)(fluoroalkylcarbonyl)amide, halide, nitrate, nitrite, sulfate, hydrogensulfate, alkyl sulfate, aryl sulfate, carbonate, bicarbonate, carboxylate, phosphate, hydrogen phosphate, dihydrogen phosphate, hypochlorite, and an anionic site of a cation-exchange resin. 63-64. (canceled)
 65. The system according to claim 52, wherein the anion of the functional ionic liquid is selected from the group consisting of bis(methanesulfonyl)amide, bis(trifluoromethanesulfonyl)amide, bis(benzenesulfonyl)amide, or bis(p-toluenesulfonyl)amide.
 66. (canceled)
 67. The method according to claim 52, wherein the cation of the functional ionic liquid is dicationic or polycationic.
 68. The method according to claim 52, wherein the anion of the functional ionic liquid is dianionic or polyanionic.
 69. The system according to claim 52, wherein the Lewis acid gas is CO₂ and the cation-Lewis-acid-gas complex is a cation-CO₂ complex.
 70. The system according to claim 52, wherein the first zone comprises a flue gas scrubbing zone.
 71. The system according to claim 52, wherein the second zone comprises an anode compartment of an electrochemical cell.
 72. The system according to claim 52, wherein the complexation agent comprises copper.
 73. (canceled)
 74. The system according to claim 52, wherein the cation of the functional ionic liquid comprises N-butylethylenediaminium bis(trifluorosulfonyl)amide.
 75. The system according to claim 52, wherein the first zone comprises at least one diluent liquid. 76-78. (canceled) 